High Efficiency Energy Harvesters in 65nm CMOS Process for Autonomous IoT Sensor Applications

Two integrated, highly efficient RF-to-dc rectifier circuits are presented. The rectifier circuits are based on improved Dickson charge pump models and are fabricated using 65-nm CMOS GlobalFoundries process. The designs utilize diode-connected metal-oxide-semiconductor field-effect transistors instead of the conventional Schottky diodes to provide a fully integrated circuits. A detailed analytical model that supports the improved circuit model is given. The measurement results of both rectifier circuits show good agreement with the simulation results. The fabricated rectifiers' start to operate at -17.5-dBm input power. The tested frequency of operation of the rectifier circuits is 953 MHz (GSM900 band), however, other frequency bands such as 2.4 GHz (Bluetooth/WLAN) could be covered with proper impedance matching. The measured peak power conversion efficiency (PCE) of the implemented rectifiers are 84.37% and 56.16% at input power levels of -12.5 and -15 dBm, respectively. To the best of our knowledge, this is the highest achieved PCE for the class of rectifiers at such low input power level in the literature. High sensitivity and excellent PCE of the presented rectifiers are ideal for utilization in wireless sensor network, Internet of Things, energy harvesting, and biomedical applications.